Cold therapy devices have been used for a number of years to reduce the swelling in the body, especially after a surgery. It has been proven that the application of cold therapy to a surgical site immediately after surgery reduces the post surgical swelling about the site and can reduce recovery time. Cold therapy devices can range in technology from a simple ice pack to an electronically cooled unit having a plurality of precise controls and features. This application is concerned with units which pump a chilled fluid through a pad which is placed in close relationship to the surgical site. In general, such devices come in two basic forms. In one form a portable ice chest having a quantity of ice and water placed therein and an internal pump is used to pump cooled liquid through the patient pad. In a second form, a precisely controlled thermoelectric module is used to cool a quantity of liquid placed within a reservoir and pumped to the patient pad.
Currently, electronically controlled units are typically used in institutions due to their costs, and the portable ice chests are used as a take home device so that a patient can continue the cold therapy at home. Some institutions, in an effort to eliminate the capital costs associated with the larger units, have begun using the small portable units immediately after surgery and then send the unit home with the patient. The patient is charged for the take home unit. However, as described, the portable units use ice to chill water within the ice chest which requires frequent checking and recharging with a new quantity of ice. Therefore, the nurse or attendant must keep a watchful eye on the ice in the ice chest so that the patient will get the full benefit of cold therapy. The melt time of the ice is further enhanced by the heat generated by the small motor which generally extends into the ice chest to pump fluid from the chest to the pad. Further, the take home units are primarily designed for use in the home, after the patient has rehabilitated a few days in the hospital, and therefore have few controls. Immediately after surgery, the site may still be numb and the patient would be unable to determine if the fluid is too cold. While cold therapy is advantageous, it is possible to cool the tissue too much and thereby discourage healing or cause possible tissue damage. After the patient is home, he/she should have full feeling at this site and will be able to tell when the liquid is too cold. While the large institutional units employ precise temperature controls to prevent excessive cooling, the smaller take home units generally can only control the temperature of the liquid by restricting the flow of water through the pad.
The institutional units use large thermoelectric modules which use electricity to chill the liquid to its desired temperature. However, while these thermoelectric modules are well suited to maintain the temperature at the desired level, they require large amounts of energy to initially cool the liquid. Further, while the thermoelectric modules are cooling the liquid, they generate significant heat which must be blown out of the unit by electric fans to prevent the electronics from overheating and to prevent the simultaneous heating and cooling of the liquid.